The present invention relates to a pneumatic tire and an assembly of a tire and a wheel. More particularly, the present invention relates to a tire and an assembly of a tire and a wheel, which are adapted to improve operationality for mounting a tire on a rim.
Heretofore, there has been proposed a pneumatic tire, in which a heel diameter of a bead portion is made slightly smaller than a heel diameter of a rim to tightly mount the bead portion on the rim, thus the bead portion is adapted not to fall off easily from the rim even if a high pressuring force is applied thereto due to an impact from the side and the like in addition to a large driving force or braking force during running.
However, with regard to such a pneumatic tire, since a mounting pressure in mounting the same on the rim is greatly increased, it takes time to mount the tire on the rim, thus causing a low rim-mounting operationality.
The object of the present invention is to provide a pneumatic tire and an assembly of a tire and a wheel, which are capable of improving operationality for mounting the tire on a rim while favorably maintaining a capability of the tire in resisting falling-off from the rim.
The pneumatic tire of the present invention for achieving the foregoing object, which has a bead core buried in a bead portion, is characterized in that a ratio dw/D of an inner diameter dw of the bead core to a heel diameter D of a rim, which is specified in a public standard, and a ratio dt/D of a heel diameter dt of the bead portion to the heel diameter D of the rim satisfy the following inequalities:
1.009 less than dw/D less than 1.022 
0.980 less than dt/D less than 0.996 
Meanwhile, the assembly of the tire and the wheel of the present invention for achieving the foregoing object, which comprises: a pneumatic tire having a bead core buried in a bead portion; and a wheel provided with a rim for attaching the bead portion of the tire, is characterized in that a ratio dw/D of an inner diameter dw of the bead core to a heel diameter D of the rim and a ratio dt/D of a heel diameter dt of the bead portion to the heel diameter D of the rim satisfy the following inequalities:
1.009 less than dw/D less than 1.022 
0.980 less than dt/D less than 0.996 
While the ratio dw/D of the inner diameter dw of the bead core to the heel diameter D of the rim is increased in the above-described manner, the ratio dt/D of the heel diameter dt of the bead portion to the heel diameter D of the rim is reduced, thus a thickness of a rubber interposed between the bead core and the rim is increased. Accordingly, in mounting the bead portion on the rim, it is possible to execute the mounting at a low pressure based on the elasticity of rubber. Moreover, after the mounting, in addition to frictional resistance between the rubber under the bead core and the rim, a high mounting force is obtained because the heel diameter dt of the bead portion is small, thus the falling-off of the bead from the rim is hard to occur. Accordingly, when the ratio dw/D and the ratio dt/D are set as described above, the operationality for mounting the tire on the rim can be improved while favorably maintaining the capability of the tire in resisting falling-off from the rim.
In the present invention, the rim applied to the pneumatic tire is a rim specified in a public standard (JIS, TRA and the like).